Here's some help on improving the strength of your switches (as descibed in ESE-SCC do-it-yourself document, I'm still half-way (no progress in the past year :-() in building an ESE-SCC with 512kb s-ram)
The upper right corner of the konami print is only used as GND. If you cut out a corner, you can made room to place your switch on top of the cartridge (make half a hole in both front and backpanel). If you use a ZIF socket you will also need to cut a big hole in the frontpanel of your cartridge. Hope this helps, Bastiaan Hubers -----Original Message----- From: Richard Atkinson <[EMAIL PROTECTED]> Newsgroups: local.msx.int Date: Friday, March 01, 2002 4:05 PM Subject: 4Mbit Flash SCC cartridge details >Well Hans, I'm quite sure you could reproduce the unit given just the >information in the previous mail, but for documentation purposes and for >the benefit of the non-technically inclined, here's how it works. > >It's a very simple mod; all it does is convert the pinout of the 28 pin >1Mbit mask ROM socket to fit the 32 pin Flash ROM chip (requires >re-routing of A16 and Vcc, and OE# held low) and adds the top two bits >using the switches. I have a single side of A4 on which I drew the 28 pin >socket pinout and marked in the pins which needed to be changed and a >small sketch of the switch circuit, and together with Sean's pinouts.txt >that's all I used for the project. I'll attempt to summarise the switch >circuit using ASCII art. > > +5V > | > / +------- A17 > \ R | (on SCC chip) > / ..o > | .. > A17 -------+-----o o >(on 32 pin socket) > o > | > _ > - > GND > >That's my first ever "useful" ASCII diagram, by the way. The switch is a 3 >position with centre position "off". When it is in the upper position, A17 >is connected to the SCC A17 output (it is pulled up by R but this >shouldn't matter as long as R is large enough). When it is in the middle >position A17 is pulled high. When it is in the lower position it is >grounded. This gives the functionality described in the previous mail. >There is an identical circuit for the A18 address line. > >The choice of R caused me the most difficulty (!) - at the moment it is >2K2 and this works fine but probably places an unnecessary load on the SCC >chip outputs (and the MSX power supply). 4mA worst case is just wasted. >After some discussion on the IRC channel, I decided 10K was a good >trade-off between low noise and power consumption, but you are of course >free to choose any value you think appropriate. > >I am going to make one or two minor "tweaks" to this project in the coming >weeks, to make it easier to use. You are welcome to include these ideas in >your designs from the outset. Firstly, I will obtain a 32 pin ZIF socket >and put it in the existing 32 pin socket so that Flash ROM chips are >easier to exchange. Secondly, I will investigate ways of mounting the >switches that are a bit stronger (at the moment they are physically >supported by the pull-up resistors!). Thirdly, I will think about adding a >pull-up resistor to OE# and putting a switch in for that line, so that the >cartridge is switchable in the usual SCC sense. I will almost certainly >replace the existing 2K2 pull-ups with 10K ones when I make these changes. > > >Richard > >-- >For info, see http://www.stack.nl/~wynke/MSX/listinfo.html -- For info, see http://www.stack.nl/~wynke/MSX/listinfo.html
